Control system



Sept. 8, 1936.

C. FREESE "CONTROLASYSTEM Filed 001:. 27, 1934 New 5m with? Clyde H. Freese, deceased, late of Nishayuna,

3%., by Ruth Rodlsey Freesa-exccutrix, Nisliaynna, N. Y, assignor to General Electric Company, a corporation oi New York Application (October 27, 193%, Serial No. 35%,293

15 Claims.

This invention relates to control systems, more particularly to systems for controlling a plurality of movable objects, and it has for an object the provision of an inexpensive, simple, reliable and improved system of this character.

I More specifically, the invention relates to systerns for controlling objects which are located at a distance from each other, and a further object is the provision of a satisfactory control in whichthe number of inter-connecting control conductors is reduced to a minimum.

In carrying the invention into efie'ct in one form thereof, each of a plurality of objects, situated remotely from each other, is provided with an electro-responsivecontrol device, and these devices are under the control of a single, controlling circuit. These control devices are additionally provided with inter-locking means for exercising a control over the control circuit such that all of the controlled objects are caused to operate in substantial correspondence with each other. In

' a specific embodiment of the invention, each of the controlled objects is driven by suitable driving means, such as an electric motor, and the control devices are arrangedto stop the motors in predetermined positions of the controlled objects and to transfer the control of restarting of the motors to the control circuit. The control devices are provided with means which prevent the restarting of the motors until all of the controlled objects have been moved to positions of correspondence, and thus the controlled objects are operated step by step in substantial correspondence with each other.

Another aspect of this invention relates to a motor control system in which a plurality of main driving motors, remotely located from each other, are to be controlled from a common control point. These motors may be alternating current slip ring induction type motors, reduiring both primary and secondary control. A further object of this invention is the provision of suitable means, utilizing a minimum number of control conductors between a common control station and the controlled motors ior effecting both primary and secondary control of these motors.

In carrying this aspect of the invention into effect in one form thereof, the master speed controlling switches of the main driving motors are operated by suitable means such as by pilot motors, which are controlled to operate step by step in substantial correspondence as set forth in the foregoing description of the broader aspect of the invention.- The primary control of the main driving motors is eflected by means of a the following specification and to the accompany-t ing drawing, the single figure of which is a simple, diagrammatical illustration of an embodiment of the invention. In illustrating the invention in one form thereof, it is shown as embodied in a cable spinning control in which an aerial tramway cable ill is passed around two traction sheaves it and 92 by means of which the aerial tramway is driven as the successive layers of the bridge suspension cable are laid. The aerial tramway cable it may be utilized for laying the cables of a suspension bridge to be built across a body of water, such as a bay or river represented by the two parallel lines H3. The sheaves ii and i2 are driven by any suitable driving means, such for example as electric motors i l and it, the drive shafts of which are direct connected to the sheaves ii and 52 respectively. Although these motors may be of any suitable type, they are preferably alternating current slip-ring wound rotor induction motors and are supplied from a suitable source, represented in the drawing by the three supply lines it. The motor to may be connected to the supply source it for rotation in either the forward or reverse direction by suitable reversing switching means illustrated as forward and reverse contactors ll and. i3. Similar contactors l9 and 20 are provided for connecting the motor ltto the source for rotation in the forward and reverse directions respectively.

In the application illustrated, it is clear that the driving motors l6 and it should operate at substantially the same speeds and it is, therefore, desirable'that the starting, stopping and running operations of these motors should be controlled from a common control station. The primary and secondary control means for each driving motor are preferably arranged adjacent the motor which they control, and thus control conductors between the common control station and the controlling means for each driving motor are necessary. In some instances, the traction sheaves ii and 52 abledistance, often in excess of a mile. In such 30 26 to short circuit the resistance 28.' In this conchances of control cable failure increase in proportion to the number of conductors, and a minimum number of control conductors is therefore desirable. In the arrangement shown, three con-f half-wave rectifying devices 44 and 45 are control wires are utilized between the control station and the remotely located motor. The control wire 2| extends from the control station on the left-hand 'or near side acrossthe body of water l3 and controls the primary reversing contactors l9 and 20 of the remote driving motor l5. A second control wire 22 extends from the control station to the remote motor and is utilized tocontrol its master speed controlling switch and a third wire 23 is utilized as a return.

The speed controlling master switches of the traction motors I4 and I5 are illustrated as multiposition drum switches 24 and 25 respectively provided with contact means 26 and 21 for controlling the sec'ondaryresistances 28 and 29 respectively of the motors M and I5, thereby to control their speeds. The master switches 24 and 25 are illustrated as motor-operated switches. Thepilot motor 30 is geared to rotate the drum of the switch 24 and is also provided'with a suitable driving connection for moving the contact means nection, it is pointed out that the structure of f the master switches 24 and 25 may be very different from the structure illustrated. Usually the structure and circuit arrangement of these switches is very complex and for this reason the switches 24 and 25 are illustrated conventionally and diagrammatically for the purpose of simplification. Preferably the pilot. motor 30 is of the alternating current type and is arranged to be connected to the supply source l6 for operation in either the forward or reverse direction by means .of suitable directional switching means illustrated as forward contactor 3| and reverse contactor 32. The forward contactors 3| on the near side and 34 on the far side respectively when energized and closed cause the pilot motors 30 and 33 torotate the master switches 24 and 25 in such a direction as to increase the speed of the motors l4 and '|5 and are, therefore, referred to as the fast contactors. Thegreverse contactors 32 and 35 cause the pilotmotors to rotate the master switches in a direction to decrease the speed of the main driving motors and are, therefore, referred to as the "slow contactors. I

In order that both forward and reverse contactors I9 and 20 for the remote traction motor l5 may be controlled by means of the'single control conductor 2| from the control station on the near side, the half wave rectifying devices 36, 31 and 38 are included in the circuit of this conductor in parallel relationship with each other on the near side and two similar half-wave rectifiers 39 and 49 are also included in-the circuit in parallel relationship with each other on the far 'side. These half-wave rectifying devices may be of any suitable type but are preferably of the surface contact type such for example as the wellknown copper oxide rectifying device. Suitable electro-responsive relay devices 4| and 42, the operating coils of which are respectively'included in circuit with the rectifying devices 39 and 48 are provided for controlling the operation of the forward and reverse contactors l9 and 28 of the remote traction motor l5. A suitable master switching means illustrafedas a manually operated master switch 43 having forward and reverse positions is provided on the near side for controlling the operation of the relays 4| and 'f 42 on the far side.

For the purpose of controlling both fast and slow ,contactors 34 and 35 on the far side from I the control station on the near side by means of a single conductor 22, two reversely connected nected in the circuit of thi conductor in parallel relationship witheach other on the near side and similar reversely connected half wave rectiflying devices 46 and 41 are connected in the cirfying devices 46 and 41 respectively on the far side are provided for controlling the fast and slow contactors 34 andw35 respectively. The relays 4|, 42,-

48, and 49 are preferably copper jacketed for the I purpose of providing'a time delay in their dropout operation so that they will remain closed for a short interval of time after their energizing circuits have been interrupted. These relays are illustrated conventionally, however, as provided with dash -pots for'efiecting the time delay in their drop-out operation.

In order to insure the operation of the traction motors I4 and I5 on corresponding speed points of their master switches, positioning relays 58 and 5| are respectively provided in the control apparatus on' the near and far sides respectively. These relays are under the respective control of the master switches 24 and 25, and they function to stop the pilot motors 30 and 33 respectively in predetermined positions of the master switches 24 and 25 respectively. These relays. 50 and 5| also function to restore control ofthe restarting of the pilot motors 30 and 33 to controlv conductor 22,

. and in addition these relays 50 and 5| are so interlocked with the control conductor 22 that they prevent restarting of the pilot motors until both master switches 24 and 25 have come to rest in predetermined corresponding positions. Thus, if the two master switches do not operate in synchronism, the faster operating switch must always stop when it reaches a predetermined position and wait until the slower operating master switch has reached a corresponding position. It

will thus be seen that the control is such as to efiect step-by-step operation of the master switches 24 and 25 in substantial correspondence with each other.

With the above understanding of the apparatus and connections and their organization in the completed system, the operation of the system itself will be readily understbod from the following detailed description:

rectifier 38, conductor 58, upper pair of stationary contacts of traction motor master switch 43,

bridged by the movable contact member 43., operating coil of under-voltage relay 55 and thence by conductors 59 and 50 and line switch 52 to the middle supply line l8. Since the rectifier 38 passes only half-wave rectified current, the under-voltage relay 55 is provided with means for providing a time .delay in its drop-out operation. This means is conventionally illustrated as a dash-pot, but preferably the relay is constructed with a copper jacket to provide the necessary time delay action. In responding to energization, re-' lay 55 closes both its contacts. If it is desired to operate the traction motors J4 and |5 in the forward direction the master switch 43 is moved to its right-hand or forward position, in which it completes an energizing circuit for the operating coils of under-voltage relay 5| and the forward traction motor relay 4| for the remote traction motor. This circuit extends from the conductor 51, through rectifier 35, third and fourth stationary fingers of master switch 43 bridged by movable contact member 43, lower contacts of undervoltage relay 55, conductor 52, near side limit switch 53, stationary contacts 54, bridged by contact 25-, conductor 55, coil of under-voltage relay 5|, control conductor 2|, far side limit switch 56, stationary contacts 51 bridged by movable contact member 2h, conductor 58, rectifier 39, coil of relay 4|, and thence by return conductor 23 to conductor 55 and the middle line of the supply source l6. Since the rectifier 39 and the rectifier 35 th conduct current in the same direction, the forward relay 4| is energized. The rectifier 40, however, does not conduct current in the same direction as the rectifier 35 and consequently the reverse relay 42 is not energized at this time, and cannot be energized until the master switch 43 is operated toits reverse position to connect the reversely connected rectifier 31 in circuit. In responding to energization, the under-voltage relay and forward relay 4| close their contacts. In the forward position of the master switch 43, the energizing circuit of under-voltage relay 55 is interrupted. However, since this relay is provided with time delay in its drop-out action, its contacts remain closed until the upper contacts of under-voltage relay 5| close to complete a holding circuit for the operating coil of relay 55 inde-' pendently of the master switch 43. The lower contacts of relay 5| complete an energizing circuit for the forward contactor ll of the near side traction motor N. This circuit is traced from the conductor 51, through lower contacts of relay 5|, conductor 69, second and third (from the bottom) stationary fingers of switch 43, bridged by movable contact 43c, conductor 10, upper closed interlocks of reverse contactor 8, operating coil of forward contactor l1 and thence by conductors 1| and 50 to the middle supply line l5. 0n the far side, the contacts of forward relay 4| in closing complete an energizing circuit for the forward contactor l9, which circuit extends from the to the supply source l5 for rotation in the forward multi-position masterdirection. Since the switches 24 and 25 are on the same speed point, i. e., their first positions, with the entire amount of the resistances 28 and 29 in circuit, the traction motors H and I5 commence to rotate at slow speed. In the closed position of the forward contactors I1 and 9, stationary interlock contacts I1. and |9a are respectively bridged by movable interlock contacts "a and I91 thereby completing a holding circuit across stationary contacts 54 and 51 of the master switches 24 and 25 respectively. This particular feature prevents the directional contactors for the motors I4 and I5 from being energized unless both master switches 24 and 25 are in the first position. Thus, with this interlocking arrangement provided for the primary control, if under-voltage occurs or if any safe-run button is opened while the traction motors are operating, then both traction motors will be deenergized and cannot be restarted until both master switches 24 and 25 have been returned to the first position and the master switch 43 has beenreturned to its off position to reenergize the under-voltage relay 55.

In order to increase the speed of both traction motors l4 and I5, the spring actuated master switch I5 is moved to its right-hand or fast" position, to complete energizing circuits for the fast relay TI on the near side and fast relay 48 on the far side. The energizing circuit for the relay 48 is traced from the conductor 5'! through the contacts of normally closed switch 18, which is preferably of the push-button type, rectifier 44, upper pair of stationary fingers of master switch 15 bridged by movable contact member 165, intermediate stationary contacts of position relay 5! bridged by movable contact member 59., conductor 19, operating coil of interlocking relay 80, control wire 22, lower stationary contacts of positioning relay 5|, bridged by stationary contact 5's, rectifier 45, operating coil of fast relay 48 and'thence by the return conductor 23 to the opposite side of the supply source. Interlocking relay 80- and fast relay 48 close in response to energization. Since rectifier 41 does not-conduct current in the same direction as rectifier 44, the slow relay 49 is not energized at this time and cannot be energized until master switch 15 is actuated to its left-hand position to connect the reversely connected rectifier 45 in circuit with rectifier 41 and operating coil of relay 49. In the closed position of interlocking relay 89, its lower movable contact completes the energizing circuit for fast relay 11, which circuit is traced from the, upper supply line IE to conductor 8|, lower stationary contact of positioning relay 50 bridged by movable contact member 50b, conductor 82, normally closed contacts of switch 53 which is preferably a push-button type switch, conductor 84, intermediate contacts of interlock relay 80 bridged by the lower movable contact member, second and third (from the bottom) contacts of master switch 15, bridged by movable contact member 15, operating coil of fast relay 1! and thence to the opposite side of the supply source. Fast relay closes in response to energization.

In the closed positions of fast relay 1'! on the near side, and fast relay 48 on the far side, en-

and thence by conductors ii and 68 to the opposite side of the supply source. Theenergizing circuit for the fast contactor St on the far side extends from the upper side of the supply source it through switch 55, conductors ti and 8%, contacts of relay t8, conductor 89, upper closed interlocks of slow contactor 85, operating coil of fast contactor 35, upper contacts of master switch 25 bridged by segment 25;, conductor 98 and thence by conductor 15 to the opposite side of the supply source It. In responding to energizetion, the fast contactors 3i and 36 close and connect the pilot motors 30 and 33 respectively to the supply source 15.

Pilot motors 36 and 33 now begin to rotate in such a direction as to move the movable contacts 26 and 21 respectively in an upward direction to short circuit the resistances 28 and 29 respectively and thus to increase the speeds of the traction motors i l and it.

The pilot motors 3B and @533 will rotate at substantially the same speeds, but inpractice one of these motors may rotate slightly faster than the other. This would be undesirable because the master switch driven by the faster operating pilot motor would tend to cause the traction motor controlled thereby to rotate faster than the traction motor controlled by the master switch driven by the slower operating pilot motor. Since both traction motors i l and it are connected to a common load, it is desirable that both shall operate on the same speed points of the master switches and at approximately the same speed. Assuming that the pilot motor 83 rotates slightly faster than the pilot motor at, the movable contact member 25b of the master switch 25 will bridge its cooperating stationary contacts, slightly before the movable contact member 2% bridges its cooperating stationary contact. As a result, an energizing circuit is completed for the operating coil of the positioning relay bi extending from the top supply line it through switch 55, conductor iii, intermediate stationary contacts of contactor 3d bridged by movable contacts 3 3a, operating coil of relay 5 i, stationary contacts of controller 25'bridged by movable contacts 251 and thence by conductors 9t and M to the opposite side of the supply source it. In responding to energization, positioning relay 5i closes its upper contact thereby completing a holding circuit for operating coil of contactor 3 3 extending from conductor 8?, through upper contacts of relay bi,

' lower contact of contactor 36, operating coil of contactor 3t and thence by conductors es and it to the opposite side of the supply source. At the same time, the energizing circuit for East relay 68 previously traced through the lower sta tionary contacts of relay Si is interrupted. Relay iii opens its contact and thus interrupts the energizing circuit for fast oontactor 8d. The latter, however, remains energized through the holding circuit established by positioning relay ti. Thus at this point in the operation, the control of the fast contactor 534i and thereby the secondary, control of the traction motor iii is taken away from the fast relay fit and is taken over by the master switch 25 and the positioning relay 5i.

Since the operating coil oi the interlocking relay 3G is in circuit with the operating coil of the fast relay 38, the opening of the lower contact of positioning relay iii deenergizes the relay be. The relay til opens in response to deenergization, but the energizing circuit of the fast relay ii on the near side previously traced through the in- Zi termediate stationary contacts oi relay all is aosaear maintained through the independent holding circuit established by its own lower interlock contacts.

Since the pilot motor 39 is operating at a speed o'nlyslightly slower than that of pilot motor 33, the movable contact 2% engages its cooperating stationary contacts, a very slight interval of time after the engagement of movable.

contacts 25b with its cooperating stationary contactand while they are-still in engagement with each other. Engagement of the movable contact 26s with its cooperating stationary contacts completes an'energizing circuit for the operating coil or the near side positioning relay 50, which circuit is traced from the power conductor 8| through intermediate interlock contacts of fast contactor Si, operating coil of positioning relay 58, stationary contact of master switch 26 bridged by movable contact 261, and thence by conductors 85, ii and 6b to the opposite side of the supply source. Positioning relay to opens its lower contact to interrupt the energizing circuit of fast relay ii and also opens its intermediate contactfrom power conductor 89 through upper station-' ary contacts of relay 56, lower interlock contacts of fast contactor 3i and from this point to the opposite side of the supply source as previously traced. Thus, it will be observed that at this point 85 and thereby the control of pilot motor 3b and the secondary control of traction motor as are taken away from the fast relay ii and transferred to the master switch 2 5 and the positioning relay 5t.

As the drum switch as continues to rotate from position a to position b, the movable contact 25b is moved out of engagement with its cooperating stationary contact thereby interrupting the energizing circuit for positioning relay bi. The movable contact Elia of relay bi drops out of engagement with its cooperating upper stationary contacts thereby to interrupt the energiaing circuit of the fast contactor 3G, which opens to disconnect the pilot motor from the supply source iii, thereby stopping the master switch 25 'in the operation, the control of the fast contactor in position b and causing the speed of the traccooperating stationary contact therebyrto inter-' rupt the energizing circuit for the positioning re! lay to, whose movable contact 5% descends out of engagement with its cooperating upper stationary contact to interrupt the holding circuit for the fast contactor 88 which in turn opens to disconnect the pilot motor 3b from the supply source it and to stop the master switch 26 in position b which corresponds with pontion b or the master switch 25 on the far side. The traction motors l4 and I are now operating at substantially the same speed on corresponding speed points of their master switches. The movable contact 503 reengages its cooperating intermediate stationary contact to recomplete the previously traced energizing circuit for interlocking relay 80 and fast relay 48 on the far side, whilst movable contact 50b engages its cooperating lower stationary contacts to reestablish the previously traced energizing circuit for the fast relay 1'! on the near side. The relays 11 and 48 respond to restart the pilot motors 30 and 33 in the manner previously described and the master switches 24 and 25 are actuated from position b to position 0.

As the master switches again approach predetermined positions in which movable contacts 24 and 25c respectively engage their cooperating stationary contacts, the control is again taken away from the fast relays l1 and 48 and is transferred to the master switches 24 and 25 and position relays 50 and Si. I When the faster operating master switch reaches its 0 position, its pilot motor is stopped until the slower operating master switch reaches its corresponding position, and the control is retransferred to the fast relays 1'! and 48.

When the traction motors I4 and I5 are operating at the desired speed, the spring actuated master switch 16 is returned to its central or off position in which the energizing circuits for the fast relay H, the interlocking relay 80 and the fast relay 48 are interrupted .which in turn open the fast contactors 3i and 34 to stop the pilot motors 3d and 33. The traction motors I4 and i5 continue to operate at a substantially constant speed, the value of which is determined by the positions of the master switches 24 and 25. It is to be noted that the segments 24s and 25a serve as limit switches for automatically stopping the pilot motors 3t and 33 when the master switches 2 and 25 reach their last positions.

If it is desired to reduce the speed of the traction motors M and it, the spring actuated master switch it is operated to its left-hand or slow position in which energizing circuits are com pleted for the slow relay 39 on the far side and the slow relay 92 and interlocking relay 80 on the near side. The circuit for slow relay 49 is traced from the power conductor 5? to normally closed contacts of the push-button l8, rectifier 35, second and third (from the top) stationary contacts of master switch it bridged by movable contact lite, intermediate contact of positioning relay 50 bridged by contact 5%, conductor 19, operating coil of interlocking relay 36, control conductor 22, normally closed contact of positioning relay 5i, rectifier ll, operating coil of slow relay $9 to return conductor 23. Since rectifier 46 does not conduct current in the direction in which rectiher it is conducting, the fast relay 48 is not energized at this time. The circuit for the slow relay 9? on the near side isreadily traced. from conductor at through lower normally closed contacts of positioning relay 5t, conductor 82, normally closed contacts of switch 83, conductor 85, intermediate contact of interlocking relay 80 (closed in response to energization), lower pair of contacts of master switch it bridged by movable contact The, operating coil of slow relay 92 to conductor t8 and the opposite side of the supply source. Slow relays 92 and 49 now close their contacts to complete energizing circuits for the slow contactors 82 and 35 on the near and far sides respectively, thereby causing pilot motors til and 33 to rotate the master switches in the reverse direction and reinsert the resistances 28 and 29 in the secondary circuits of the traction motors l4 and i5 to reduce their speed. As in the previously described operation, the master switches 24 and 25 are operated step by step in substantial synohronism with each other. The circuits established for providing this step by step operation for the speed decreasing operation are similar to those already described for the speed increasing operation and are obvious from the previous description.

Thus,- the interlocking arrangement between the master switches on the near and far sides is such that if the two master switches are not operating in synchronism, the faster operating switch must always stop when it reaches each of a plurality of predetermined positions and wait untiLthe slower operating master switch reaches a corresponding position. This is provided by the positioning relay 5! on the far side preventing the directional relays 71 and 92 on the near side from being energized and similarly by positioning relay 5!] on the near side preventing the relays 48 and 49 on the far side from being energized as long as the positioning relays are energized.

Ii' it is desired to operate the traction motors l4 and IS in the reverse direction, the directional master switch 43 is moved to its left-hand or reverse position. In the central or "01? position of' master switch 43, the previously described energizing circuit for under-voltage relay 56 is completed and this relay is closed. In the reverse position of the master switch 43, the energizing circuits are established for the reverse relay 42 on the far side and reverse contactor E8 on the near side. The circuit for the reverse relay 42 on the far side is traced from power conductor 51 through rectifier 3'3, contacts or" master switch 43 bridged by movable contact 13d and thence by the circuit previously traced for the forward relay 46 to the points between rectifiers 39 and :36 at the far side, through rectifier dd, operating coil of reverse relay 32 and thence to the return conductor 23. Undervoltage relay iii and reverse relay 62 close to complete energizing circuits for reverse contactor it on the near side and reverse contactor 2% on the far side, respectively. The circuit for contactor it? extends from the power conductor 5? through lower closed contacts of under-voltage relay Si, lower pair of contacts of master switch 13 bridged by movable contact 43s and thence by conductor 93 and normally closed upper interlocks of forward contactor ii, through operating coil of reverse contactor it, and thence by conductors ii and til to the opposite side of the supply source. The energizing circuit for the reverse contactor 26 is traced from the upper supply line it through conductor l2 and contacts of reverse relay d2 through conductor 94 and upper normally closed interlock of forward contactor ihthrough operating'coil of reverse contactor 2B and thence by conductor id to the opposite side of the supply source. Since'rectifier 39 does not conduct current in the same direction as rectifier til, the forward relay il cannot be energized at this time. The remaining operations are the same as those described for the forward operation.

Indicating lamps t5 and 9d are provided at the control station for respectively indicating whether the near side master switch 2 3 and the far side master switch 25 respectively are operating properly. The circuit for the near side indicating lamp 95 extends from the upper supply line I 6 to conductor 8i, through lower stationary contact of positioning relay 58, through conductor 82,

lamp to and conductors 5d and at to the opposite side of the supply source. The circuit for far side indicating lamp as is traced from power conductor 8! through lower contacts of relay 8@ and lamp 98 to the opposite side of the supply source. When the master switch 26 is at points between its predetermined positionapositloning relay till is deenergized and the circuit for lamp as is completed. Similarly when the master switch 25 on the farside is at points in between predetermined positions, positioning relay Si and consequently interlocking relay so are deenergized so that the circuit for the lamp at is completed. This feature is desirable because it gives the'oporator a visual indication of the operation of both. master switches 26 and 25.

When both traction motors i l and i5 are deenergized, the master switches 26 and 25 are automatically returned to their ofi position provided the control switch it is in the OE position. For example, if the directional master switch 453 is moved to its central ofi position from either of its operating positions to deenergize the directional contactors for the traction motors at a time when the master switches 26 and 25 are on any speed points beyond their first points, the slow contactors 32 and 35 are energized. With both directional contactors ll and it open, the energizing circuit for the slow contactor 32 is traced from the upper supply line it, through conductor Bl, lower interlocks of contactors l8 and l! in series, upper interlocks of fast contaotor 38, operating coil of slow contactor 32, intermediate pair of stationary contacts of master switch 24% bridged by segments 2d: and thence, by conductors 86, ll and 60 to the opposite side of the supply source. A similar circuit for the slow contactor 35 on the far side is traced from upper supply line i8 through conductor 81!, lower normally closed interlocks of contactors 20 and i9 in series, conductor 97, upper interlocks of fast contactor 36, operating coil of slow contactor 35, intermediate stationary contacts of drum switch 25 bridged by movable contacts 25: and thence by conductors 96 and i l to the opposite side of the supply source. Slow contactors 32 and 35 close and connect pilot motors 3d and 33 respectively to rotate the master switches 26 and 25 toward their low speed position. When the master switches 26 and 25 reach their low speed positions, the energizing circuits for the operating coils of the slow contactors 32 and 35 are respectively interrupted by contact segments 2d! and 25: and the contactors open to disconnect and stop the pilot motors 3d and 83. Thus, the master switches 26 and 25 are restored to their first position when the traction motors i 0 and is are deenergized and thus the system is restored to a reset position.

In addition, means are provided for operating either of the master switches 26 or 2?) independently of the other. This feature is provided by push button switches i6 and 83. If the pushbutton switch is is depressed into engagement with its lower cooperating stationary contacts, the control circuits for the far side, previously traced through the upper stationary contacts are interrupted whilst the control circuit is established through the lower stationary contact by means of which the near side pilot motor 3d and drum switch 2 3 can be operated. independently. Similarly if push-button 88 is depressed out oi engagement with its cooperating stationary contacts, the control circuits for the near side pilot motors to previously traced through these contacts is interrupted and the far side pilot motor 33 and drum switch- 25 can be independently operated by means of the control circuit extending through the upper stationary contacts of push button switch it.

Although in accordance with the provisions of the patent statutes, this invention is described as embodied in concrete form,vit will be understood that the apparatus and connections shown and described are merely illustrative and that the invention is not limited thereto since alterations. and modifications will readily suggest themselves to persons skilled in the art without departing from the true spirit of this invention and the scope of the annexedclaims.

What is claimed as new and desired to secure by Letters Patent of the United States, is:--

1. A control system comprising a plurality of controlled objects, a common control circuit therefor, a separate electro-responsive control device connected with each of said objects, means for selectively controlling the direction of operation of said objects and interlock means in said circuit controlled by said control devices for effecting operation of said objects in the selected direction in substantial correspondence with each other.

2. A control system comprising a plurality of movable objects, a control circuit therefor, a separate control device in said circuit for each of said objects, means for selectively controlling the direction of movement of said objects, and means responsive to the positions of 'said objects for controlling said control devices to efiect movement of said objects in the selected direction in substantial correspondence with each other.

'3. In a control system for a plurality of movable objects, a common control circuit for said objects, a plurality of electro-responsive devices in said circuit, one associated with each or said one of said driving means, means connected to,

said circuit and actuated by said controller for controlling the direction of operation of the other of said driving means, means responsive to a predetermined amount of movement or one of said objects for stopping its associated driving means, means responsive to a predetermined amount of movement of another of said objects for stopp. its associated driving means and cooperating with said first mentioned position responsive means for restarting said driving means.

5. In a control system in which two movable objects are simultaneously operated, separate driving means for each of said objects, a common control circuit, a directional controller for one of said driving means, means included in said circuit and actuated by said controller for controlling the direction oi operation of the other of said driving means, means responsive to movement of the faster 'moving object to a predetermined position for stopping said faster moving object at said positions, and means responsive to movement of the slower moving object to a corresponding predetermined position for stopping said slower moving object and cooperating with said first mentioned position responsive means for restarting both said objects in said selected direction.

6. A control system in which two objects are .moved simultaneously comprising separate driving means for each of said objects, a control circuit common to both said driving means, a relay responsive to thernovement of the faster moving object to predetermined positions for stopping its driving means, a relay responsive to move-- ment of the slower moving object to corresponding predetermined positions for stopping its driv ing means, and an interlocking relay in said circuit actuated by both said position responsive relays when said objects are in corresponding predetermined positions for restarting said driving means so as to cause said objects to operate in substantial correspondence with each other.

I. A control system in which two objects re motely situated with respect to each other are simultaneously moved, comprising separate driving motors for each of saidv objects, individual tial correspondence with each other.

8. A co-ntrol'system in which two remotely situated objects are moved simultaneously comprising individual driving motors for objects, a common control circuit for said motors, a pair of control relays in said circuit, one for each of said motors, a ccntactor for each of said motors controlled; by each of said relays, means responsive in a predetermined position of the faster moving object for stablishing a holding circuit for the contactor controlling its motor and rendering its relay ineffective and responsive in a second position for stopping and retransferring the control of said contactor to said relay, and means responsive in a predetermined position of the slower moving object for establishing a holding circuit for the contactor controlling its motor and rendering its relay ineffective and preventing restarting of the motor for said faster moving object until said second object has moved to a position corresponding to said second position and responsive in said corresponding position for returning control of said contactor for its motor to its control relay.

9, A control system in which two objects remotely situated with respect to each other are,

controlled from a common control station, comprising individual driving motors for each of said objects, a common control circuit for each of said motors, electroresponsive means associated'with each of said motors for controlling the direction of rotation thereof, means for energizing said electroresponsive means for operation of said motors in a selected direction comprising a pair of reversely connected rectifying devices associated with each of said objects and included in said circuit and means for selectively energizing one rectifier of each of said pairs, and means responsive in predetermined positions of said objects to take control of said motors from said circuit and operable in certain other corresponding positions to stop said motors and to return control of the restarting thereof to said circuit.

10, A control system for a plurality of motors remotely situated with respect to each other comprising directional switching means for each of said motors, a common control circuit for said motors, means for actuating the switching means for one of said motors to effect rotation thereof in a selected direction comprising a pair of reversely connected rectifying devices associated with each of said motors and included in said circuit and a controller for selectively actuating corresponding rectifying devices of each of said pairs, said controller being provided with means for controlling the actuation of the switching means for the other of said motors to effect rotation thereof in a corresponding direction, individual mvlti-position switching means actuated by each of said motors for taking control of said direc tional switching means mom said circuit in predetermined positions of said multi-position means to stop said motors and for returning the control of the restarting of said motors to said circuit, and means controlled by said multi-position switching means for preventing restarting of said motors'until all or" said inulti-position switching means are in corresponding positions.

ii. A motor control system comprising aplurality of motors, directional switching means for each of said motors, a common control circuit therefor, a directional controller and means controlled thereby for selectively actuating the direc tional switching means of one of said motors, means included in said circuit and actuated by said controller for selectively actuating the directional switching means of the other of said motors, a plurality of rculti-position switching devices, one associated with each of said motors and actuated thereby for taking over control of said motors from said circuit and for stopping said motors in predetermined positions of said switches and returning the control of restarting said motors to said circuit and means con rolled by said switches for preventing restarting of each of said motors until all of said switches are in corresponding positions.

12. A motor control system comprising a plurality of movable objects, an individual motor for driving each. of said objects, directional contactors for each of said motors a common control circuit for said contactors, a relay having its operating coil in said circuit for controlling each of said contactors, means for taking over control of said contactors from said relays to stop said motors in successive predetermined positions of said objects and to retransfer the control of said contactors for restarting said motors to said relays comprising a plurality of multi-position switching devices each actuated by a 'corresponding one of said motors and a separate relay controlled by each of said switching devices and contacts in ,said circuit actuated by each of said separate relays for preventing restarting any oi said motors until all of said objects are in corresponding positions so that all of said motors oper= ate step by step in substantial correspondence with each other.

13. A motor control system comprising a pinrality of motors remotely situated with respect to each other, forward and reverse switching means for each of said motors, a master switch associated with one of said motors, a pair of re- ,trol circuit from said master switch to the forward and reverse switching means of said remote motor, reversely connected rectifying devices in circuit with said master switch providing. for selective operation of the forward and reverse switching means of said remote motor in response to operation of said master switch, an individual multi-position master switch for each of said motors'and actuated thereby for stopping said motors in predetermined positions of said multi-position switches and subsequently transferring control of restarting said motors to said circuit, and means in said circuit controlled by said multi-position switches for preventing restarting of said motors until all of said multiposition switches are in corresponding positions.

14. A motor control system comprising a pair of main driving motors remotely located with respect to each other, a multi-position master switch connected with each of said motors for controlling its speed, an individual pilot motor of said pilot motors; directional switching means,

controlled by said circuit for controlling the direction of rotation of said pilot motor to increase and decrease the speed of said main driving motors, switching meanscontrolled by said master switches for taking over control of said pilot motors from said circuit to stop said motors and ing positions whereby said master switches are operated step by step in substantial correspondence.

15. A motor control system comprising a pair of main driving motors remotely located with respect to each other, a multi-position master switch for controlling the speed of each of said motors, an individual pilot motor for driving each of said master switches, a common control circuit for said pilotmotors, means for simultaneously controlling the direction of rotation of said pilot motors to increase or decrease the speeds of said main motors, electro-responsive switching means operable in predetermined positions of said mas ter switches for taking over control of said pilot motors from said circuit to stop said motors and subsequently to restore control of the restarting of said pilot motors to said circuit, and contacts in said circuit controlled by electro-responsive switching means for efiecting restarting of said pilot motors only after all of said master switches have been operated to corresponding positions thereby providing step by step operation of said master switches in substantial correspondence and 

